Spray drift, or off-target drift, is an increasingly important concern of the agricultural industry. Spray drift is the movement of herbicides or other sprayed agricultural treatment material away from the target area resulting in wasted material, possible damage to nearby crops and plants and/or pollution of local surface water. When agricultural compositions are sprayed onto crops, a drop size distribution results. While small drops, typically defined as less than 150 microns, traditionally provide better crop coverage, they are also more prone to drifting. Large drops, commonly regarded as those with diameters greater than 400 microns, tend to resist drift but are prone to bouncing off crop surfaces resulting in reduced coverage and effectiveness. The optimum drop size range for minimizing drift and maximizing deposition effectiveness is generally considered to be 200-400 microns.
Reducing the amount of small droplets can significantly reduce spray drift. This is currently being achieved by employing new nozzle technology or through the use of relatively high molecular weight water-soluble polymers as antidrift agents. Antidrift additives include acrylamide homopolymers and copolymers, polysaccharides such as guar, guar derivatives and xanthan gums and polyalkylene oxides such as polyethylene oxides. One problem with these and other known antidrift additives is that they are often difficult to dissolve in water. A second problem is that the larger drops that they produce tend not to adhere well to the target crops.